为什么 Firebase 用户在刷新时不再经过身份验证？

Question

一个非常简单的应用程序。在/ 路径上，我想在登录时呈现Home，如果未登录，则呈现Introduction。在登录页面上登录有效，如果我 console.log(firebase.auth().currentUser) 它显示所有数据和/ 正确呈现Home。因此，虽然仍在/ 路径上，但发生了一些奇怪的事情；当我刷新页面时，我们不再登录，它呈现Introduction。但是当我单击链接<li><Link to='/'>Home</Link></li> 时，Home 组件会正确呈现，并且我们会再次登录。为什么会这样？

import React, { Component } from 'react';
import {BrowserRouter as Router, Route, Switch, Link, Redirect} from 'react-router-dom';
import firebase from './firebase'

import Home from './containers/home'
import Login from './containers/login'
import Register from './containers/register'
import Dashboard from './containers/dashboard'

const Protected = ({component: Component, ...rest}) => (
  <Route {...rest} render={(props) => {
    if(firebase.auth().currentUser) 
      return <Component {...props} />
     else 
      return <Redirect to='/register' />

  }} />
)

const Introduction = props => ( <h1>hello</h1>)

class App extends Component {


  render() {
    return (
      <Router>
        <React.Fragment>
          <ul>
            <li><Link to='/'>Home</Link></li>
            <li><Link to='/register'>Register</Link></li>
            <li><Link to='/login'>login</Link></li>
            <li><Link to='/dashboard'>dashboard</Link></li>
          </ul>
          <Switch>
            <Route path='/' exact render={(props) => {
              if(firebase.auth().currentUser) 
                return <Home {...props} />
              else
                return <Introduction {...props} />
              }
            } />
            <Route path='/register' exact component={Register} />
            <Route path='/login' component={Login} />
            <Protected path='/dashboard' component={Dashboard} />
          </Switch>
        </React.Fragment>
      </Router>
    );
  }
}

export default App;

Answer 1

会发生什么：

• 网页加载
• Firebase 启动请求以检查用户是否已通过身份验证
• 应用呈现，currentUser 为空
• 身份验证状态发生变化，但应用不会重新渲染

应用需要监听身份验证状态的变化并相应地执行重新渲染。 https://firebase.google.com/docs/reference/js/firebase.auth.Auth#onAuthStateChanged

class App extends React.Component {
  state = {
    currentUser: null
  }

  componentDidMount() {
    this.unsubscribe = firebase.auth().onAuthStateChanged(currentUser => {
      this.setState({ currentUser })
    })
  }

  componentWillUnmount() {
    this.unsubscribe()
  }

  render() {
    // use this.state.currentUser
  }
}